Electric discharge apparatus



June 12, 1945. M N 2,378,222

ELECTRIC DISCHARGE APPARATUS Filed Jan. 12, 1943 Inventor; George E.Inman,

by W H Attorney.

Patented June 12, 1945' Emo'rmc DISCHARGE APPARATUS George E. Inman,East Cleveland, Ohio, asslgnor to General Electric Corn New York pany, acorporation of Application January 12, 1943, Serial No. 472,103

9 Claims.

My invention relates to electric discharge apparatus and particularly tocircuits for electric discharge devices having rectifyin properties,such for example as rectifying fluorescent lamps. It is the object of myinvention to provide an improved circuit for the operation of aplurality of such devices with a minimum amount of equipment Myinvention will be better understood from the following description takenin connection with the accompanying drawing, and its scope will bepointed out in the appended claims.

Referring to the drawing, Figs. 1, 2, 3, 4 and 5 are circuit diagrams;Fig. 6 represents by way of example only one form of discharge 'deviceorlamp such as is shown diagrammatically in Figs. 1, 3 and 5.

In Fig. 1, I have represented at I, 2, 3 and 4 four similar dischargedevices which, for example, may be fluorescent lamps like that shown inFig. 6. The lamp shown in that figure is of small size being rated at 4watts and being adapted to operate at about 12 volts. It comprises the3-contact base 5 and the evacuated refractory envelope 6 containing asmall amount of mercury and a rare gas such as argon at low pressure,the inner surface of the envelope being coated with a suitablefluorescent material. The lamp has the filamentary cathode I which maycomprise a coiled coil of tungsten wire coated with a mixture of bariumand strontium oxides. The ends of the cathode connect by the supportingleads 8 extending through the insulating block 9 of the base with one ofthe external contacts I thereof and with the shell I3. Within theenvelope and spaced from the cathode is the anode II, shown as a wirering having the supporting lead l2 by which it connects with the otherexternal contact II). By reason of the above described construction thelamp passes current substantially in only one direction; hence, it isrectifying.

The lamps in Fig. 1 may be considered as comprising two similarlyconnected pairs, lamps I and 2 being one pai i and lamps 3 and 4 beingthe other pair. The two pairs are connected in series to be suppliedthrough the control switch I4 from the source of alternating current Iwhose voltage may have a range of 38-44 volts. The lamps of each pairare connected with the source with the one in reverse to the other;hence, being rectifying in character, they pass opposite half cycles ofthe current supplied. It will be seen that the current passing betweenthe cathode and the anode of lamp I passes through the cathode of lamp 2and likewise the current passing between the cathode and the anode oflamp 2 passes through cathode of lamp I. The same is true of lamps 3 andI. The cathode of each lamp has suflicient resistance and has sufllcientcurrentcarrying capacity to properly ballast the other lamp associatedwith it forming the pair. It also allows the other lamp of the pair tooperate at full current. Although I have illustrated the series circuitin Fig. 1 as comprising only two pairs of lamps it will be understoodthat it may comprise many more pairs than illustrated depending upon thevoltage of the source.

Although the voltage of the source will cause the lamps to continue tooperate after having been started it is insufficient to cause them tostart unless their cathodes are heated to an elec tron emittingtemperature. Heating of the oathodes preferably is effected by passingthrough them current taken from the source. For controlling this currentIhave shown the starting switches I8 and II, the former connectedbetween the cathodes of lamps I and 2 and the latter connected betweenthe cathodes of lamps 3 and .4, whereby when the main switch It isclosed cathode preheating current flows from the source through thecathodes of the four lamps in series. The temperature of the cathodesquickly rises to the point of electron emission after which the openingof the switches I6 and I1 applies the full voltage of the source acrosslamps I and 3 in series and across lamps 2 and 4 inseries. The lampspresumably start and continue to operate with lamps I and 3 operating onone-half cycle and lamps 2 and 4 operatin on the other half cycle. Iprefer to have the starting switches open automatically. In Fig. 1, Ihave shown them as normally closed thermal switches of the bimetallictype each having a resistance heater I8 connected to be traversed by thecathode preheating current, the construction of the switch and heaterbeing such that by the time the lamp cathodes have become suificientlyheated by the current flow therethrough the starting switches will open.Thereafter the passage of lamp current taken by the lamps 2 and throughthe heaters provides the heat necessary to maintain those switches open.

In Fig. 2, I have shown the circuit comprising a single pair of positivecolumn rectifying lamps 20 and 2|, the two lamps of the pair beingreversely arranged as in Fig. 1. The circuit also includes the thermalstarting switch 22 having the heater 23 connected to be heated by theoathode preheating current and in this case by the current supplied toboth lamps.

Inasmuch asthe cathode a positive column lamp of common construction maynothave suflicient resistance to properly ballast the other lamp, I haveshown the circuit provided with the additional ballast 24 in the form ofa reactor. The source of supply IS. in this case may bean ordinarylighting circuit of 118 volts or higher depending upon the dimensions ofthe lamps. a

In that form or my invention illustrated by Fig.

'3 the lamps are arranged in two series circuits connected in parallelwith each other, the lamps in one circuit operating on the positivehali' cycles 0! the supplied alternating current and the lamps in theother circuit operating on the negative halt cycles. Thus lamps 2, 21,28, 29 and 30 form one series circuit and may be considered as operatingon the positive half cycles of the supply current and lamps 3|, 3!, l3,l4 and 35 form another series circuit operating on thenegative halfcycles. The two series circuits are connected in parallel with eachother and are supplied through the single ballast reactor 24' and themain switch 14 from the source i which may be a 118 volt lightingcircuit. The circuit may be thought of as comprising a plurality ofpairs of lamps, such for example as lamps a and 3t, lamps 21 and 32,etc., one lamp of a pair operating on one half cycle and the otheroperating on the other half cycle. For preheating the lamp cathodesby'current flow therethrough the cathodes of each pair of lamps areconnected together by thermal switches as before, the switches beingrepresented at 36, 31, 3B, 89, and ll. These switches, however, functiononly to control the flow of cathode preheating current as they do notopen until after the lamps have started. The switches 36-40 inclusiveare provided respectively with the heaters "-45 inclusive which areshown connected in series respectively with the anodes of lamps 26-30inclusive. In this form of my invention when the main switch is closed,current flows in series through the ballast 24', the cathodes of all ofthe lamps and all of the thermal switches. After the cathodes havebecome heated by this current fiow the voltage applied across each lampfrom the source is suiiicient to cause it to start. The how of lampcurrent through the several heaters then causes the thermal switchesassociated therewith to open thereby cutting oil the flow or preheatingcurrent to the cathodes.

Fig. 4 illustrates a form of the circuit shown in Iii Fig. 3 whichincludes a single pair of positive column lamps represented at 4! and48. The circuit otherwise is similar to that of Fig. 3.

In Fig. 5 I have shown a form of my invention inwhich the rectifyinglamps are operated from a source of direct current. The lamps are shownat and BI and the source of direct current is represented as comprisingthe two batteries 52 and 53. Battery I! has its positive terminalconnected through the cathode of lamp 80 and through the switch M withthe anode of lamp ii and has its negative terminal connected with theanode of lamp II and with one end 0! the cathode oi lamp Ii, whereby thebattery 52 supplies operating current to lamp II through the oathode oflamp 50, which cathode functions as the ballast. Similarly the battery53 has its positive terminal connected through the cathode of lamp 5|with the anode of lamp ill and its negative terminal connected with theanode of lamp BI and with the cathode of lamp SI so that it suppliesoperating current to lamp Bl through the cathode of lamp ii whichcathode functions as the ballast. Upon closing the switchfl'd,preheating current flows in a series circuit including the twobatteries, the switch, and the two cathodes. When the cathodes'havebecome sufllciently: heated the lamps start, lamp "being operated by thebat tery l8 balla'sted by the cathode of lamp SI and lamp 5! beingoperated by the battery. 52 ballastedb the cathode of lamp 50. I

For convenience in the specification and claims I refer tothe cathodesoi the discharge devices as resistive and as iilamentaryJHoweven-I donot desire to belimited to such cathodes as I may employ devices havingcathodes provided with separate resistive heaters o'fj-Well known formin which case the cathodes'are preheated by current flow through theheaters instead or through the cathodes themselves and in the case 01'those terms of my invention illustrated by Figs. 1, 2 and 5 the cathodeheater of 'one device performs a ballasting iunctionior another device.

r I have chosen'the particular embodiment described above asillustrative otrmy invention and it will be apparent thatvarious-modifications may be made without departing irom the spirit andscope of my invention which modifications I aim to cover by the appendedclaims.

What I claim as new anddesire to secure Letters Patent of the UnitedStates is:

1. In combination, a plurality of electric discharge devices connectedtobe operated in parallel from a source of current supply each having ananode and a resistance cathode, means connecting with the anode of eachdevice for supplying the device with operating current through thecathode of another device, whereby said cathodes function as ballast forsaid devices.

2. In combination, a plurality of electric discharge devices and meansconnecting said devices to be operated in parallel from a source ofcurrent supply each device having an anode and a resistance cathode,said means connecting the anode of each device through the cathode ofanother device with said source of current supply, whereby the cathodeof each device functionsas ballast for another device.

3. In combination, a plurality of electric discharge devices each havingan anode and a resistance cathode constructed to be preheated bycurrenttherethrough, means connecting said anodes to be supplied withoperating current from the opposite sides respectively of a source ofalternating'current; the anode of each device being connected throughthe cathode of the other device, ands switch connected between saidcathodes to control the flow of heating current thereto and to controlthe starting orsaid devices.

4. In combination, a plurality of rectifying electric discharge lampseach having an anode and a filamentary cathode, means connecting theanode of each lamp with one end of the filament of the other lamp, meansconnecting the other ends of said filaments-each with one side of asource of alternating current, and athermal switch responsive to thelamp current connected between said anodes.

5. In combination, a plurality of rectifying electric discharge lampseach having an anode and a filamentary cathode, means connecting theanode of each lamp with one end of the filament oi the other lamp, meansincluding a ballast impedance connecting the other ends of saidfilaments each with one side of a source of alternating current, athermal starting switch connected between said anodes. and a heatertherefor connected to be energized by the lamp current.

6. In combination, a plurality of rectifying electric discharge deviceseach having a cathode constructed to be preheated by current flowtherethrough, means connecting said devices in parallel and with one inreverse t0 the other to be supplied from a source of alternatingcurrent, and switching means connecting said cathodes in series to besupplied with heating current from said source.

7. In combination, a plurality of rectifying electric discharge deviceseach having a cathode constructed to be preheated by current flowtherethrough, means connecting said devices in parallel and with one inreverse to the other to be supplied from a source of alternatingcurrent, a switch connecting said cathodes in series to be supplied withheating current from said source, and an actuator for said switchconnected to be responsive to lamp current.

8. In combination, a plurality of rectifying electric discharge lampseach having a filamentary cathode, means connecting said lamps inparallel and with one in reverse to the other, means including a ballastimpedance for connecting said parallel-arranged lamps with a source ofalternating current, a thermal switch connected between said cathodes inseries to be supplied with preheating current from said source, and aheater for said switch connected to be responsive to lamp current.

9. In combination, a plurality of rectifying electric discharge lampseach having an anode and a filamentary cathode, means connecting theanode of each lamp with one end of the filament or the other lamp, meansincluding a ballast reactor for connecting said anodes respectively withthe opposite sides of a source of alternating current, a thermalstarting switch connected between the opposite ends of said filaments,and a heater for said switch connected in series with one of saidanodes.

GEORGE E. INMAN.

